Coloured angiogram (blood vessel X-ray) of the skull of a 37 year old female patient that has had a stroke. The stroke, or cerebrovascular accident (CVA), was caused by a thrombosis (blood clot) in the right middle cerebral artery, a branch of the right internal carotid artery in the neck shown here. The stroke has caused hemiparesis (weakness) of the left side of the body. Treatment is thrombolysis, which uses drugs to dissolve the blood clot.